1. Field of the Invention
The present invention relates to a chain guide including a guide shoe slidingly guiding a running chain and a base member supporting the guide shoe along a chain running direction.
2. Description of the Related Art
A chain guide provided with a guide shoe that slidingly guides a running chain is commonly used for stabilizing the chain that runs between sprockets and maintaining the correct chain tension.
For example, FIG. 16 shows a well-known timing system of an engine in which a transmission chain CH such as an endless suspended roller chain is caused to run between sprockets S1, S2 provided at a crankshaft and a camshaft, respectively, inside an engine room. The timing chain CH is endless suspended between the drive sprocket S1 mounted on the crankshaft inside the engine room E and a pair of driven sprockets S2 mounted on the camshaft, and the timing chain CH is guided by a swinging guide G and a chain guide 500 (fixed guide).
In such a well-known timing system, the chain guide 500 is fixed inside the engine room E by two mounting shafts B1, B2, and the swinging guide G is mounted inside the engine room such as to be capable of swinging in the suspension plane of the timing chain CH about the swinging shaft B0 as a center.
A chain tensioner T maintains the correct tension of the timing chain CH and inhibits vibrations by applying pressure to the swinging guide G.
In the chain guide used in such a well-known timing system, the running guide portion is preferably configured of a low-friction wear-resistant material, and a chain guide entirely configured of a low-friction resin material is known.
However, the fixed chain guide should be strong, rigid, and durable enough to ensure stable guiding against the tension and vibrations of the chain, and when the chain guide is configured only from a resin material, the material thickness should be increased to obtain the necessary strength, rigidity, and durability, and the space occupied by the chain guide inside the engine room increases.
Accordingly, a configuration is known (Japanese Patent Application Publication No. H10-89428) in which only the running guide portion is formed from a low-friction resin material, and this resin material is supported by a material with high strength, rigidity, and durability, such as a metal, thereby reducing the occupation space, while ensuring the strength, rigidity, and endurance necessary for the chain guide as a whole.
For example, as shown in FIGS. 17 to 19, the well-known chain guide 500 includes a guide shoe 510 made from a resin and slidingly guiding a running chain and a base member 520 made from a metal and supporting the guide shoe 510 along a chain running direction.
The base member 520 is constituted by a shoe support portion 521 extending in the chain running direction and base mounting portions 522 extending vertically at positions set apart with respect to the chain running direction. The two base mounting portions 522 are formed by bending at 90° with respect to the shoe support portion 521 from an integral metal sheet.
The two base mounting portions 522 are each provided with a mounting hole 523 for inserting a fixing member such as a pin or a shoulder bolt.
The guide shoe 510 is configured such that a running guide portion 511 is supported by the shoe support portion 521 of the base member 520, and end locking pieces 512 at both ends in the chain running direction and a plurality of side locking pieces 513 provided at appropriate locations in a width direction can be fitted by locking to the shoe support portion 521 and detached.
A lip 519 for introducing the chain so that the chain could be correctly mounted along the running guide portion 511 when the chain is assembled and for controlling the chain movement in the width direction when the chain is used is provided at each side of the running guide portion 511.